braindump shader thoughts

Author: arocull

godot/addons/stag_toolkit/utils/shader_includes/include_colorspace.gdshaderinc

@@ -1 +1,2 @@
 #define LINEAR_TO_RGB(r, g, b) vec3(pow(##r, 2.2), pow(##g, 2.2), pow(##b, 2.2))
+// https://github.com/godotengine/godot/issues/70927

godot/addons/stag_toolkit/utils/shader_includes/include_normals.gdshaderinc

@@ -0,0 +1,18 @@
+// https://blog.selfshadow.com/publications/blending-in-detail/
+
+// Returns a world-space Tangent Bitangent Normal matrix
+// https://gamedev.stackexchange.com/questions/178606/how-to-calculate-normal-from-normal-map-in-world-space-opengl
+mat3 world_normal_matrix(
+	in mat3 model_normal_matrix, in vec3 model_tangent,
+	in vec3 model_binormal, in vec3 model_normal
+) {
+	vec3 T = normalize(vec3(model_normal_matrix * model_tangent));
+	vec3 B = normalize(vec3(model_normal_matrix * model_binormal));
+	vec3 N = normalize(vec3(model_normal_matrix * model_normal));
+	return mat3(T, B, N);
+}
+
+vec3 parse_normal_map(in vec3 normal_map_value, in mat3 tbn) {
+	return normalize(tbn * normalize(fma(normal_map_value, vec3(2.0), vec3(-1.0))));
+}
+

godot/addons/stag_toolkit/utils/shader_includes/include_remap.gdshaderinc

@@ -1,8 +1,8 @@
 // Remaps a value from a given range to a new range
 float remap(in float value, in float in_min, in float in_max, in float out_min, in float out_max) {
-	return out_min + (value - in_min) * ((out_max - out_min) / (in_max - in_min));
+	return fma(value - in_min, (out_max - out_min) / (in_max - in_min), out_min);
 }
 // Remaps a value from 0 to 1 to a new range
 float remap_fast(in float value, in float minimum, in float maximum) {
-	return minimum + value * (maximum - minimum);
+	return fma(value, maximum - minimum, minimum);
 }